This study is directed at a deeper understanding of the epithelial matrix interactions of the DMBA induced mammary tumor. The specific aims are to study: a) the type of collagen synthesized by the epithelial and stromal elements of this tumor, b) the effect of hormone environment on the synthesis and turnover of collagen from these elements, c) the effect of collagen inhibitors such as cis-hydroxyproline on the hormone dependent and independent DMBA tumor growth in vivo.